Conventional bellows-type pumps utilize a reciprocating flexure element, such as a metal bellows, which draws fluid into and forces fluid out of a chamber during each cycle of the bellows action. The bellows is typically connected to a solenoid actuator drive or a reciprocating rotary drive mechanism.
Examples of solenoid-actuated bellows-type pumps are described in U.S. Pat. No. 2,797,646 to Pomykata and U.S. Pat. No. 2,849,159 to Kaufmann. A rotary drive bellows-type pump is described in U.S. Pat. No. 2,419,775 to Hazard.
U.S. Pat. No. 2,257,862 to Sarver describes a bellows-type pump having two bellows, each bellows being connected to an electromagnetic actuator. The two bellows surround a common fluid chamber and flex out of phase to alternately expand and contract the chamber.
U.S. Pat. No. 4,365,942 to Schmidt describes a liquid helium bellows-type pump which utilizes two fixed electrical coils near the end walls of a fluid chamber and a third electrical coil attached to a movable piston located within the fluid chamber. The piston is attached to a bellows at each of its ends. The interaction of the electromagnetic fields among the three coils causes the third coil and the attached piston to oscillate within the chamber to generate the pumping action of the bellows.
All of the conventional bellows-type pumps utilize drive mechanisms which require either sliding or rolling frictional contact among various parts. Pumps of such design thus require various types of bearings in order to function properly. In addition, lubrication may be required to produce reasonable pump life.